1. Field of the invention
The present invention relates to a coating method, specifically to a method for coating a vehicle body in order to form a coating resistant to a chipping.
2. Description of the Prior Art
A specific portion of an external surface of the vehicle body, for instance, a lower side portion of the vehicle body is likely to be hit and damaged by stones, sand, various agent dispersed on a road surface and the like while running resulting in a chipping of a coating. Conventionally, there has been known a method for forming an anti-chipping coating on such specific portion of the external surface as undercoating thereafter forming an intercoating and a face coating as taught by Japanese Patent Public Disclosure No. 58-273, laid open to the public on Jan. 5, 1983.
Japanese Patent Public Disclosure No. 57-190057, laid open to the public on Nov. 22, 1982, also discloses a method for making an anti-chipping coating. Japanese Patent Public Disclosure No. 59-160572, laid open to the public on Sept. 11, 1984 discloses a polyurethane base coating material as employed for an anti-chipping coating.
A vinyl chloride resin has been employed for making the anti-chipping coating. Recently, one-can type urethane (blocked polyurethane coating material) is often used as the anti-chipping coating because the vinyl chloride resin has a high viscosity which make it difficult to get a coating surface of a desirable smoothness.
The one-can type urethane coating material for the anti-chipping coating may cause an undesirable surface roughening of the resultant coating in the vicinity of a peripheral portion of an area in which the anti-chipping coating is formed. In view of the above, it has been known that a tape is applied on a potential portion of the vehicle body to prevent the coating from the surface roughening wherein the tape is removed after the anti-chipping coating for enabling an intercoating step.
It will however be understood that this method is disadvantageous in efficiency because the number of steps is increased.
There has been proposed so called wet-on-wet method for forming an anti-chipping coating without using tape in which an intercoating step is carried out before the anti-chipping coating is dried up.
This method is advantageous in the point that the anti-chipping coating material is draped with the intercoating material to eliminate the problem of the surface roughening without using any tape.
It should however be noted that the wet-on-wet method is disadvantageous in the following point. Namely, a solvent of the undercoating material or anti-chipping coating material is dispersed into the intercoating material to lower a viscosity of the intercoating material thereby causing a sagging of the coating to deteriorate an appearance of the coating.
In order to eliminate the problem, it may be effective to reduce a thickness of the anti-chipping coating. This causes a different problem in which a chipping resistance property is undesirably lowered.